The present invention relates in general to a solid-state image sensing device and, in more particular, to a swing-driven solid-state image sensor which vibrates relative to incoming image light to increase the number of sampling points in one frame image, which contributes to an improvement in the resolution of the image sensor.
An easy method for obtaining high resolution of a picked-up image in a conventional solid-state image sensor such as an interline transfer type CCD (to be referred to as an IT-CCD hereinafter), in accordance with the interlacing image pickup technique, is to increase the number of pixels. However, even a conventional IT-CCD having a standard number of pixels has a larger chip size than many LSIs. When the number of pixels in such a CCD is increased to satisfy the need gor higher resolution without increasing the packing density, the chip size thereof becomes larger. In addition, when the number of pixels is increased while the conventional CCD chip size is kept unchanged, the packing density of the pixels must be enhanced greatly (e.g., more than four times). It is technically difficult to prepare such a high-density CCD. Even if development of improved fabrication techniques allows the manufacture of such a CCD in the near future, the circuit configuration for driving such a CCD is complicated and power consumption is high, thus entailing new problems.
In order to solve the problem concerning the number of pixels vs. packing density, the CCD is periodically displaced relative to incident image light, thereby picking up a high-resolution image. In two field periods constituting one frame period in the NTSC system, when the CCD is swung at an amplitude corresponding to 1/2 the pixel pitch such that pixels are positioned in different sampling positions along a horizontal direction, the apparent number of spatial sampling points along the horizontal direction can be doubled. Therefore, the horizontal resolution of the one-frame image can be substantially doubled even if a conventional low-resolution IT-CCD chip is used.
According to a solid-state image sensing device for performing the aforementioned swing image pickup, a mechanism must be held together with the IT-CCD chip in a single package unit to effectively swing the IT-CCD chip in a desired vibration mode. Piezoelectric elements such as bimorph piezoelectric elements are used to minimize the vibration loss of CCD chips having a larger chip size than the conventional LSI chips and to generate a maximum effective vibration. However, it is difficult to pack the piezoelectric elements and their electrical connections together with the CCD chip in a single device. This is because when the common lead wire connection or normal film connector is used to electrically bias the piezoelectric elements subjected to mechanism vibrations, the connection decisively limits the vibration of the piezoelectric elements.